The compound 8-fluoro-2-{4-[(methylamino)methyl]phenyl}-1,3,4,5-tetrahydro-6H-azepino[5,4,3-cd]indol-6-one represented by formula
is a small molecule inhibitor of poly(ADP-ribose) polymerase (PARP). 8-Fluoro-2-{4-[(methylamino)methyl]phenyl}-1,3,4,5-tetrahydro-6H-azepino[5,4,3-cd]indol-6-one and salts thereof, is disclosed in U.S. Pat. No. 6,495,541 and PCT. Application. No. PCT/IB2004/000915, International Publication No. WO 2004/087713, the disclosures of which are incorporated herein by reference in their entireties. U.S. Provisional Patent Application Nos. 60/612,459 and 60/679,296, entitled “Polymorphic Forms of the Phosphate Salt of 8-Fluoro-2-{4-[(methylamino)methyl]phenyl}-1,3,4,5-tetrahydro-6H-azepino[5,4,3-cd]indol-6-one,” the disclosures of which are incorporated herein by reference in their entireties, describe novel polymorphic forms of the phosphate salt of 8-fluoro-2-{4-[(methylamino)methyl]phenyl}-1,3,4,5-tetrahydro-6H-azepino[5,4,3-cd]indol-6-one, and methods for their preparation. U.S. Provisional Patent Application Nos. 60/612,458; and 60/683,006, entitled “Therapeutic Combinations Comprising Poly(ADP-Ribose) Polymerases Inhibitor,” the disclosures of which are incorporated herein by reference in its entirety, describe pharmaceutical combinations of 8-fluoro-2-{4-[(methylamino)methyl]phenyl}-1,3,4,5-tetrahydro-6H-azepino[5,4,3-cd]indol-6-one.
To date, eighteen enzymes have been identified by DNA sequence homology in the PARP family and the biochemical and enzymatic properties of seven have been investigated: PARP-1, and PARP-2 are stimulated by DNA strand breaks, PARP-3 interacts with PARP-1 and the centrosome, PARP-4 also known as vault PARP (VPARP) is the largest PARP and is associated with cytoplasmic vaults, tankyrase 1 and 2 (PARP-5a and 5b) are associated with telomeric proteins and the function of PARP-7 (TiPARP) is not clear at present but it may be involved in T-cell function and it can poly(ADP-ribosylate) histones (Ame J C, Splenlehauer C and de Murcia G. The PARP Superfamily. Bioessays 26 882-893 (2004)). Pharmacology studies have shown that the compound of formula 1 is an inhibitor of PARP-1 (Ki=1.4 nM) and PARP-2 (Ki=0.17 nM). Based on structural similarities in the amino acid sequences among the PARP enzymes, the compound of formula 1 likely binds with high affinity to the other members of the family as well.
Enzyme-mediated repair of single- or double-strand breaks in DNA is a potential mechanism of resistance to radiotherapy or cytotoxic drugs whose mechanism depends on DNA damage. Inhibition of DNA repair enzymes is thus a strategy for the potentiation of these agents. PARP-1, the best-characterized member of the PARP family, is a nuclear enzyme that upon activation by DNA damage mediates the transfer of ADP-ribose fragments from NAD+ to a number of acceptor proteins. Depending on the extent of DNA damage incurred, PARP-1 activation and subsequent poly(ADP-ribosyl)ation mediate the repair of the damaged DNA or induce cell death. When DNA damage is moderate, PARP-1 plays a significant role in the DNA repair process. Conversely, in the event of massive DNA damage, excessive activation of PARP-1 depletes ATP pools (in an effort to replenish NAD+), which ultimately leads to cell mortality by necrosis (Tentori L, Portarena I, Graziani G. Potential applications of poly(ADP-ribose) polymerase (PARP) inhibitors. Pharmacol Res 2002; 45:73-85).
As the result of the dual role of PARP-1, inhibitors of this enzyme, such as 8-fluoro-2-{4-[(methylamino)methyl]phenyl}-1,3,4,5-tetrahydro-6H-azepino[5,4,3-cd]indol-6-one, may have a role as chemosensitizing agents (by preventing DNA repair, for example, after anticancer therapy), or as treatments for a variety of disease and toxic states that involve oxidative or nitric oxide induced stress and subsequent PARP hyperactivation. Such conditions include neurologic and neurodegenerative disorders (eg, Parkinson's disease, Alzheimer's disease) (Love S, Barber R, Wilcock G K. Increased poly(ADP-ribosyl)ation of nuclear proteins in Alzheimer's disease. Brain 1999; 122:247-53; Mandir A S, Przedborski S, Jackson-Lewis V, et al. Poly(ADP-ribose) polymerase activation mediates 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced parkinsonism. Proc Natl Acad Sci USA 1999; 96:5774-9), cardiovascular disorders (eg, myocardial infarction, ischemia-reperfusion injury) (Pieper A A, Walles T, Wei G, et al. Myocardial postischemic injury is reduced by poly(ADP-ribose) polymerase-1 gene disruption. J Mol Med 2000; 6:271-82; Szabó G, Bährle S, Stumpf N, et al. Poly(ADP-ribose) polymerase inhibition reduces reperfusion injury after heart transplantation. Circ Res 2002; 90:100-6; U.S. Pat. No. 6,423,705), inflammatory diseases, (Szabó C, Dawson V. Role of poly(ADP-ribose) synthetase in inflammation and, ischaemia-reperfusion. TIPS 1998; 19:287-98), diabetic vascular dysfunction (Soriano F G, Virág L, Szabó C. Diabetic endothelial dysfunction: role of reactive oxygen and nitrogen species production and poly(ADP-ribose) polymerase activation. J Mol Med 2601; 79:437-48), arthritis (Szabó C, Virág L, Cuzzocrea S, et al. Protection against peroxynitrite-induced fibroblast injury and arthritis development by inhibition of poly(ADP-ribose) synthase. Proc Natl Acad Sci USA 1998; 95:3867-72), and cisplatin-induced nephrotoxicity (Racz I, Tory K, Gallyas F, et al. BGP-15—a novel poly(ADP-ribose) polymerase inhibitor—protects against nephrotoxicity of cisplatin without compromising its antitumor activity. Biochem Pharmacol 2002; 63:1099-111). Furthermore, it was shown that BRCA2 deficient tumor cells are acutely sensitive to PARP-1 inhibitors (Bryant et al. “Specific killing of BRCA2 deficient tumors with inhibitors of poly(ADP-ribose)polymerase,” submitted to publication). PARP inhibitors are also involved in enhancing the induction of the expression of Reg gene in β cells and HGF gene and, accordingly, promote the proliferation of pancreatic β-cells of Langerhans' islets and suppress apoptosis of the cells (U.S. Patent Application Publication 2004/0091453; PCT Publication No. WO 02/00665). In addition, PARP inhibitors are also used in cosmetic preparations, especially in after-sun lotions (PCT Publication No. WO 01/82877). There are no marketed PARP inhibitors presently.
One method of synthesizing 8-fluoro-2-{4-[(methylamino)methyl]phenyl}-1,3,4,5-tetrahydro-6H-azepino[5,4,3-cd]indol-6-one is disclosed in the above-referenced U.S. Pat. No. 6,495,541. This method is a linear 10-step synthesis, which involves a key Leimgruber-Batcho indole formation step and a Suzuki coupling reaction. Although the current route is an effective synthetic route employed in the synthesis of toxicology and clinical batches of 8-fluoro-2-{4-[(methylamino)methyl]phenyl}-1,3,4,5-tetrahydro-6H-azepino[5,4,3-cd]indol-6-one, it would be desirable to have an alternative convergent route for eventual commercial manufacturing. The present invention provides a new and convergent route to 8-fluoro-2-{4-[(methylamino)methyl]phenyl}-1,3,4,5-tetrahydro-6H-azepino[5,4,3-cd]indol-6-one, which route is developed via a key Sonogashira coupling reaction and a CuI-promoted indole formation.